Annular muffle furnace or oven



May 26, 1925.

A. MCD. DUCKHAM ANNULAR MUFFLE FURNACE 0R OVEN Filed July. 24v, 1923 '7 Sheets-Sheet 1 May 26, 1925.

y 1,539,653 A. MCD. DUCKHAM v ANNULAR MUFFLE FURNACE 0R OVEN Filed July 24, 1923 '7 Shams-Sheet` 2 Wag-aff zz( May 26, 1925.

A. MCD. DUCKHAM ANNULAR MUFFLE FURNACE OR OVEN Filed July 24, 1923 7 Sheets-*Sheet 2&3, i925,

A. MCD. DUcKi-IAMl ANNULAR MUFFLE FURNACE OR OVEN Filed .July 24, 1925 '7 Sheets-Sheet A. MCD. DUCKHAM ANNULAR MUFFLE FURNACE OR OVEN May 26,

Filed Julyi24, 1923 7 sheets-sheet 5 24 y fi? lime/02024 A. MCD. DUCKHAM I ANNULAR MUFFLE FURNAGE GR OVEN Filed July 24, 1923 r7 Sheets-Sheet 6 May 26, 1925. 1,539,653

A. MCD. DUCKHAM ANNULAR MUFFLE FURNACE OR OVEN Filed July 24, 1923 '7 Sheets-Sheet 7 fa g Patented May 26, 1925.

UNITED STATES;

terasse I Parnu ori-us.

ARTHUR MUDOUGALL DUCKHAM, O'F LONDON, ENGLAND, ASSIGNOR TOWOODALD, DUCKHAM & JONES (1920) LIMITED, O'F LONDON, ENGLAND.

ANNULAR MUFFLE FURNACE R OVEl'.

Application led July 24, 1923. Serial No. 653,575.

Tov all 'whom t may concern:

Be it known that I, Sir ARTHUR Mo- DOUGALL DUGKHAM, a subject of the King of Great Britain, residing :in London, Eng- 5 land, hav'e'nveii-ted certain new and useful Improvements i-n Annular Muule Furnaces or Ovens, of which the Jfollowing is a specification.

This invention relates to annular inutile furnaces, ovens or kilns of the kind in which the goods lto be burnt or treated are carried on a rotating annular support which forms the lloor'of the Inutile oven or kiln and is rotated continuously or intermittently so as to bring the goods stacked upon any given part of the Hoor successively into different zones of the kiln, the arrangementbeing such that goods placed upon a portionof the floor while such portion is outside the apparatus enter the kiln at its cooler extremity,

advance towards the point of'ignition of the heating gases, and thence proceed into a portion of the kiln which is not heated, so that they may cool suiciently and slowly enough to permit Vof their being withdrawn without danger when they reach the open discharging part of theI apparatus, where they are replaced by fresh goods to be burned or treated. The invention consists in an .improved construction of mulile furnaces or kilns of this type which, by reason of the novel features hereinafter described, is of greater et'ciency in operation and has more extended application with regard to the goods which may be treated than is possible with previously proposed furnaces or this type. Amongst these eatures are novel arrangements for the supply and distribution of the heating gases, the recu erative heating of the secondary air supply for the combustion of these gases, the removal of moisture from the goods in the drying section ot the kiln. the etlicient and expeditious cooling of the treated goods, and the subsequent selective utilization of the heated air derived from the cooling zone of the furllUif. i

rl`he annular travelling door or tray of the furnace is rotated continuously or intermittently at the requisite time intervals by suitable means, as for example by means o a circular rack secured on the underside of a metal tray, which carries a refractory or insulating covering constituting the floor of the kiln, and gearing with one or more driving pinions actuated by suitable power means, the tray being otherwise supported upon rollers suitably spaced around the furnace. To obviate the tendency of the mass of material forming the insulating floor to jam owing to expansion and distortion, the insulating floor or covering of the metal tray is made in separate segments of comparatively short lengths, preferably with suitable expansion joints between adjacent sections.

i The annular kiln may be regarded as arranged circumferentially in four main sections adapted .to carry out the successive operations involved, namely loading and unloading, drying2 heating, and cooling, the

.three last sections being, however,f con-v tinuous and only the loading and'unloading sections being separated from the remainder of the kiln by the inlet and outlet doors f provided at the ends'of the annular tunnel. The goods to be treated are loaded on the exposed part of the travelling' ioor in stacks of suitable lengths, so that the doors may pass readily between adjacent stacks when raised and lowered for loading and unloading purposes.

Provision is made for grading the ternperature lof the furnace from top to bottom or so distributing the heating gases that an even temperature is maintained at all levels in the kiln, such provision cornprising a multiple arrangement of superposed horizontal dues which may be connected separately .or in pairs or multipleA with the source of heating gases at their inlet ends and with the waste gas vdue at their outlets, but are otherwise isolated from each other;

The materiaal or objects to be burnt or heat-treated are dried during an early part of their travel through the kiln by means of air. This air may be heated in a recuperator traversed by the waste gases from the kilnrand admitted to the interior of the kiln at an intermediate point and discharged through ports near the entrance door. Alternatively the goods may be dried during traverse, the kiln, e.

`walls, in close proxlmity to the heating the early part of their travel through the kiln by taking air from the lines of the cooling zone at a point near the heating zone and conducting this heated air tothe place Where it is admitted to the interior of the -kiln so as to dry and heat the goods, the

moisture-laden air being exhausted by a chimney or fan at a point near the inlet end of the kiln.

The goods are cooled by air admitted to the flues surrounding the cooling section of the kiln, and the air so heated may be utilized either as secondary air for burning the producer gases in the combust-ion flues of the kiln or for drying the goods a-s hereinbefore set outl or part ofthe air so heated may be devo-ted to one purpose and part to another. v

The cooling of the goods may be ex# pedited by introducino cold air directly into the interior of the kiln in contact with the goods at the latter part of the travel, and the air so heated may be led to the drying section of the kiln or applied to any other suitable purpose. i

To obtain a high temperature of combustion the secondary air may be arranged to g. in iues in its side gases but following an opposite course. The air which has been used for cooling the goods, or some of it, may be further heated in this manner or an increased temperature may be imparted to such air by leading it r around fines in proximity to the region of combustion of the heating gases before its discharge into the combustion fines.

In the accompanying drawings Fig. l is a sectional plan of an annular mutHe furnace or kiln embodying the present invention, and Figs. 2 and 3 are transverse sections thereof taken on diametral planes at right angles to. each other; Fig. 4 is a sectional plan sho-wing a modified construction of lfurnace; Fig. 5 is a transverse section of same on a diametral plane; Fig. 6' is a developed partial vertical section of Fig, 4 along the central line of t-he muttle; Fig. 7 is a developed partial sectional plan view of Fig. 4 on an enlarged scale; Figs. 8-18' inclusive are transverse sections on the same scale as Fig. 7' taken on the lines VIII-VIII to XVIII-XVIII respectively of Fig. 4.

Referring first. to Figs. l, 2 and?. the

I annular travelling Hoor or tray l of the inutile furnace or kiln is rotated at the ap shown, the power-developing units may be grouped in a power house situated at the centre of the kiln.

The tray 1 includes a. suliicient thickness of refractory or non-conducting material which forms the floor ot the annular inutile or kiln 6, and the latter may be regarded as comprising four main sections, namely an open or loading and unloading section A in which the root' and side walls of the kiln are absent and whiclnis separated from the muliie by a vertically sliding door 7 at the beginning or entering end of the kiln and a similar door 8 at the outlet; end of the kiln. The drying section B starts at the entering door 7 and terminates at the line B where the heating section C begins, the latter terminating at the line D', at Which point the combustion of the heating gases, supplied through the arrangement of lilies indicated at D, commences. The cooling section E extends from D to the line E, an

auxiliarv cooling section E extending from this line to the out-let door 8. It will be understood that these sections are continuous, there being no separating partitions between the several sections, the subdivision of the kiln into such sections being entirely a mat-A ter of the most suitable arrangement in each specific case of drying, heating and cooling flues. v

During the progress of the material or objects to be burnt or heat treatedthrough the section B they may be dried by means of air lintroduced into the interior of the kiln at or near the point B', this air having been previously heated by suitable means as, for example, by means' of a recuperator traversed by the Waste. gases, the drying air together with the moisture carried ott by it being discharged through suitable outlet lports placed near the inlet door 7 of the iln.

During the progress of the materialy thro-ugh the heating section S itis heated by the combustion products of the fuel gases traversing the flues 1() which aie arranged at different levels on either side of the kiln.

The heating gas, as shown in the drawings, is derived from a suitable producer 11A from which it passes along gas lines 12, 13 'to gas inlets 14 where it meet-s the heated secondary air and combustion takes place along the fiues l0 at either side ot' tlu` kiln. A motor-driven fan 16 or equivalent device such as a suitable chimney connected by the waste gas flue 17 with the waste gas outlets 9 is preferably used to maintain a suitable flow of the heating gas and rombustion products along'the heating and coinbustion fines 10. Y v

After traversing the sections C. l) the material is cooled by air admitted to the lues18 on either side ot' the cooling sertions E",- E of the kiln through air inlets lt).

Maaate j I f1: i;

This air is heated continuously in its passage alongfthe flues 18 and may have additional heatl imparted to it by being led along flues immediately adjacent to the outside of the combustion flues 10, whence it passes as secondary air to the combustion ilues, thus enabling a higher flame temperature to be obtained and simultaneously rcducing radiation losses.

|The cooling of the goods may be expedited by introducing cold air directly into the interior of the kiln at the latter part of the travel, say at the point E', and the air so heated may be discharged through suitable outlets, e. g. in the roof of the kiln in section E and thence to the drying section B for the purpose previously referred to, or applied to any other suitable purpose.

rl`he rotating floor or trayv 1 is supported by means of suitably disposed rollers or wheels such as journalled in pairs in suitable members of the xed support ofthe kiln, rails 21 fixed on the underside of the tray resting and running upon these rollers.

In the modified construction shown in general view in Figs. 4, 5 and 6' the driving gear of the rotating tray and the power-developing mechanism are omitted from the drawings, but it will be understood that the same general arrangement or any equivalent arrangement is applicable also to this construction.

The open section, that is the loading and unloading section, is as before indicated by A and extends between the inlet door 'l and outlet door 8 of the enclosed Inutile. The air drying section B extends from the inlet door 7 to the line B, at which point the drying air enters theinterior of the kiln.. The heating and burning section C extends from the line B to the line D. The air cooling section E extends from the line D to the outlet door 8 of the kiln.

The goods are dried during the early part of their travel through the kiln from the inlet door 7 by taking .air from the fiues 18 of the cooling section E at a point lnear the end of the heating section C through uptakes 22 leading to a flue 23 extending along .the top of the kiln and by-passing the heating section C to the point B where this vheated air is admitted to the interior of the air drying section and, after traversing thc same, is discharged through the Waste air i chimneys 24. near the inlet end of the kiln.

This air enters the fines 18 through the inthe VAoutlet door 8 leading to an overhead flue 30 `in the roof of the cooling section` E maybe provided, this iiue 30 discharging into the overhead by-passing fluel ot' the heating section C.

To obtain high temperatures of the scconda'ry air supplied for the combustion of the gaseous fuel delivered from the gas producer 11 through supply fines 12 to the gas inlets 14 leading to 'the flues 10 of the heating section, flues 26 may be built adjacent to the heating. and combustion flues l() of the kiln, the secondary air entering at inlets 27 and passing through the flues 2G in countercurrent to the heating gases, this heated secondary air entering the combustion and heating flues 10 at the ports 28 connecting the secondary air fiucs 21S with the said combustion `flues 1() atv points adjacent to the heating gas inlets 14. y

Thismethod of heating the secondary ai r provides a ready means of obtainiiighigh combustion temperatures and has a certain cumulative heating effect, the temperatures of the secondary air and of the `Zone ot' intense combustion being mutually reactive.

The counter-flow method of heating the secondary air may be supplemented by the use of a reciiperator heated by the waste gases as described in connection with Figs. 1 to 3, and in both constructions any ,suit- 'able arrangement of dampers may be provided at appropriate points of the drying,

heating and coolingv fines to control the 'ad-' mission or discharge of the `air and gases, and in particular to control the supply of fuel gas tothe various flues of the multiple system of combustion flue's, so that for example an even temperature or a definite gradation of temperature may be maintained from top to bottom of the'kiln.

los

The-arrangement of the air and gas fluesv inthe several sections of the kiln is shown in more detail in the enlarged sectional views of Figs. 7 to 18, in which the' various parts are designated by the same reference char-v acters as the corresponding-parts in Figs. 4 to 6.

The travelling'tray or platform of the kiln comprises a bed of iirebrick or other refractory or non-conducting material of suitable proportion carried upon transverse plate 32 extending between two concentric beams 31, the rails 21 which run iipou the rollers 20 being attached to the plates 32, and to obviate distortion of the bed consequent upon the repeated heating and cooling to which it is subjected, it is preferably made in segments A0 (Fig. 7,) of comparatively short lengths, say about' 5 feet, with cxpansion joints of suitable character between adjacent segments, or the sectional bed may be in two or more layers with the joints of adjacent sections in one layerl and staggered with respect vtvo-the Ajoints of the yadjacent sections in the 'layers immediately above or below. Alternative] the tray may be trough-shaped and fille with granular re# fractory or non-conductin material.

Apertures may be provi ed for the 'inspection of the interior of the mule chamber and its contents andV for testing the progress of the treatment by means of sample test pieces, and provision may also be made for measuring the temperature at Various points of the kiln by means of pyrometers.

The floor of the muille may be sealed fto prevent access of air from below by any known suitable means, as 'for example by a trough containing sand or even oil extending underneath` the floor adjacent to its outer and inner peripheries, side plates carried bythe floor dipping into the material contained in these fixed troughs.

It will be noted that by the arrangement -of fiues surrounding the mule hereinbefore described the'loss of heat by radiation is reduced to aminimum. The ilues therefore, in addition to their other functions, kact also as heat insulators for the mullle.

Further, it will be noted that the arrangement,` and disposition of the mechanism whereby the-loor of the kiln is rotated and supported are such that these mechanisms are practically thermally isolated from the kiln, thebdriving mechanism and the roller path and roller wheels being situated in an annular passageway below and outside the kilnv proper, and although so situated are nevertheless above ground and readily accessible for any necessary purpose, and preferably freel open to the atmosphere.j

Having thus described the nature of the said invention and the best means I know of carrying the same into practical effect, I claim 1. An annular Inutile furnace or kiln comprisinga heating section having enclosing walls separating it from the heating gases, a multiple arrangement of heating lines in said wa ls traversed by the heating gases, a plurality of gas sup ly flues leading to said heating lues, and damper means' adapted to connect the gas ilues with the heating flues in alternative parallel arrangements, the heating flues belng otherwise isolated fromfeach other along their length.

2. An annular muflle furnace or kiln-coinprising four main sections, namely an open or loading and unloading section. a drying section in which the goods are in direct contact with a stream of heated air, a heating section'lhavingmulti leV heating-gas fines and a cooling section aving multiple cooling-air,I flues.

3. An annular mutlle furnace or kiln comprising four main sections, namely an open or loading and unloading section, a drying section having enclosing walls separating it from the heating gases, a heating section Vand a cooling section, a multiple arrangesection having enclosing walls separating it` from the heating gases, a heating section and a cooling section, a multiple arrangement of longitudinal fines in the side Walls of the heating section, meansfor supplying heating gases to said fines and longitudinal air ues in the side walls of the heating section external to the gas heating flues.-

. 5. An annular muflle furnace or kiln comprising four main sections, namely-an open or loading and unloading section, a drying section, a heating section and a cooling section, a multiple arrangement of longitudinal flues in the side walls of the heating section, means for supplying heating gases to said ilues and longitudinal air flues in the roof of the heating section.

6. An annular Inutile furnace according to claim 2, comprising combustion lues for the heating gases, air lues surrounding the cooling section-.of the kiln and leading to fines adjacent to the region of combustion of the fuel gas and connections between the said flues and the combustion fines.

7. An annular Inutile furnace or kiln according to claim 2. comprising air flues surrounding the cooling section of the kiln,`

combustion flues in the heating section of the kiln, a connection between said air flues and said combustion flues and a by-pass connection from said air flues to the interior of the Adrying section of the kiln.

8. An-annula-r mulle furnace according to claim l2, comprising heating lues in thcl walls of the heating and drying sections of the kiln, air fiues in the walls of the kiln external to the said heating fines, Iand means operating to establish a flow of heating gases and of air through the respective fines in opposite directions.

`9. An annular mnffie furnace or kiln according to cla-im 2. having a travelling floor or tray constructed in separated sections ol comparatively short lengths.

10. An annular inutile furnace or kiln according to claim 2. comprising an annular travelling floor or tray, mechanism for supporting and driving the said travelling'floor,

said mechanism being open to the atmoscomprising a heating section having enclosing walls separating it from the heating gases, a multiple l:1u-rangement of heating iiues in said Walls, air iues located in the Walls of a, section of the kiln and leading to ilues adjacent to the inlet ends of'the heating fines, and connections between the said 'lues and the heating fines.

12.y An xannular muffle furnace or kiln comprising drying and heating sections having enclosing walls separating them from the heating-gases, heatin flues in the walls 10 of the said heating and rying sections, air ues in the walls external tothe said heating Hues, and means operating to establish a flow of heatin gases and of air through the respective ues in o posite directions.

In testimony w ereof I have signed my name to this specication. ARTHUR MCDOUGALL- DUCKHAM. 

